Nutrient Dense Foods: Phytochemicals Nutrient Dense Foods: Phytochemicals and Health Benefitsand Health Benefits

Alyson Mitchell, PhDUniversity of California Davis

530-752-7926http://mitchell.ucdavis.edu

Living Soil, Food Quality, and the Future of FoodAAAS Annual Meeting, February 12, 2009

Fruit and Vegetables (F&V) in the Fruit and Vegetables (F&V) in the American DietAmerican Diet

• Epidemiological studies indicate people who consume diets rich in F&V have a reduced risk of chronic diseases– stroke, type II diabetes, some cancers and potentially heart

disease

• Accordingly, AHA, AICR, NIH, CDC and USDA began promoting F&V consumption more than a decade ago– Today USDA guidelines call for 4 fruit and 5 vegetable servings

daily (USDA 2005 dietary guidelines for adults eating 2000 calorie per day)

– Americans eat ~1.4 fruit and ~3.7 vegetable servings

• Most American’s are consuming sub-optimal levels of F&V to benefit fully from the health-promoting effects of these compounds

The Obesity EpidemicThe Obesity Epidemic

BRFSS, Behavioral Risk Factor Surveillance System; http: //www.cdc.gov/brfss/

1998

2007

1990

No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% ≥30%

Increase the nutritional density of fruits and vegetables

Why Focus on Fruit & Vegetables?Why Focus on Fruit & Vegetables?

• Primary dietary source of vitamins, minerals, fiber and a wide array of non-essential nutrient phytochemicals– polyphenolic antioxidants (e.g. flavonoids), carotenoids

(e.g. lycopenes, carotenes), isothiocyanates, etc.

• The health benefits associates with F&V are largely thought to be due to the consumption and synergistic activities of these bioactive phytochemicals

• Therefore the nutrient density of bioactives in F&V has the potential to affect susceptibility to chronic disease

• Many of the critical bioactive phytochemicals found in F&V are Secondary Plant Metabolites (SPMs) O

A

B

C

Secondary Plant Metabolites (SPMs)Secondary Plant Metabolites (SPMs)

• Bioactives naturally produced by the plant usually for plant defense mechanisms– Many are potent antioxidants

• Synthesis is strongly influenced by genetics – The species and variety (cultivar) are the most important

determinants of SPM expression• Synthesis is triggered by environmental pressures

– soil quality, nitrogen availability, geographic location, climate, pest and disease pressures, field historyand UV radiation

• Therefore, cultivar selection and farming systems practices have the potential to influence the nutrient density and content of bioactives in F&V

Influenced byAgronomic Practices

Primary & Secondary Plant MetabolitesPrimary & Secondary Plant Metabolites

• Species and cultivar specific• Produced in response to environmental

pressure or plant stress

www.ualr.edu/botany/plantfactory.jpg

Phenolic Acids

Flavonoids

Alkaloids

Terpenoids

Glucosinolates

SecondaryPlant

Metabolites

SecondarySecondaryPlant Plant

MetabolitesMetabolites

Phenolic Acids

Flavonoids

Alkaloids

Terpenoids

Glucosinolates

SecondaryPlant

Metabolites

SecondarySecondaryPlant Plant

MetabolitesMetabolites

Phenolic Acids

Flavonoids

Alkaloids

Terpenoids

Glucosinolates

SecondaryPlant

Metabolites

SecondarySecondaryPlant Plant

MetabolitesMetabolites

Cultivar Differences in Phenolic AntioxidantsCultivar Differences in Phenolic Antioxidants

Gil et al. J. Agric. Food Chem. 2002, 50, 4976-4982

F&V cultivars selection should be based upon nutrient content and flavor as well as yield and disease resistance characteristics

The Logical Question?The Logical Question?

Primary PlantMetabolites

Secondary PlantMetabolites

Primary PlantMetabolites

Secondary PlantMetabolites

• Fundamental differences between organic and conventional production systems, particularly in soil fertility management and pest control– It is generally agreed that these factors can affect the

production of secondary plant metabolites (SPMs)• Do organically produced foods contain higher levels of

defense-related secondary metabolites (e.g. flavonoids) as compared to conventionally produced foods?

Complex Question to AddressComplex Question to Address

• Comparisons of organic and conventional foods are difficult to interpret for many reasons:– Difficulty to selecting farms and fields that represent the

cultivation practices– Farming systems are dynamic environments with

regional variation • Difficulty in matching soil, irrigation, climate, insect pressures,

etc– No definition of “conventional” farming

• Evolved in response to technological developments in mechanization/tillage, monoculture, synthetic fertilizer, chemical pest and weed control, and breeding

• Organic is “defined” but conditions vary dependent upon season, crop, region, pest pressures and farm philosophies

The Perception & ResearchThe Perception & Research

• Although the public perceives organic foods as being inherently more nutritious there is little scientific consciences to support this perception

• Reviews of the literature (prior to 2003) give mixed results and are difficult to interpret– Often cover large periods of time (span > 70 yrs)– Farming practices were not defined

• No information on what constitutes an “organic” food

– Lack of control in sampling, storage and analytical methods

• Retail samples with no varietal or post-harvest control• Different species of plants compared• Different plant parts were compared (e.g. a leaf with a fruit)

Studies Comparing the Nutrient Value of Studies Comparing the Nutrient Value of Organic & Conventional Foods (1970Organic & Conventional Foods (1970--2007)2007)

0

10

20

30

40

50

60

1971-1975

1976-1980

1981-1985

1986-1990

1991-1995

1996-2000

2001-2005

2006-2007

No.

of a

rticl

es

*Excludes: reviews, articles comparing soil, crop yield, contaminants, pesticides

Cropping System ComparisonsCropping System Comparisons

• Non-synthetic Pesticides– Non-specific, less potent– Increases in pest and

pathogen pressure– Increases in soil bacterial and

fungal biomass• Soil Fertility

– Organic Nitrogen– Compost, cover crops, etc– Nitrogen requiring

mineralization• GDBT

– Equilibrium between primary and secondary plant metabolism

• Synthetic Pesticides– Specific, potent– Decreases in pest and pathogen

stress– Decreases in soil bacterial and

fungal biomass• Soil Fertility

– Inorganic Nitrogen– Synthetic fertilizers– Readily available NH4+ and

NO3-• GDBT

– Emphasis on growth and production of primary plant metabolites

Organic Conventional

Soil FertilitySoil FertilityCarbon Nitrogen BalanceCarbon Nitrogen Balance

• Slow release of available nitrogen

• Plants grow more slowly• Metabolism involves the

balanced production of C containing compounds• Starch • Non N-containing SPMs• flavonoids, vitamin C

• Nitrogen surge• Rapid growth• Plants emphasizesynthesis of primary plant metabolites that contain nitrogen• growth related compounds• DNA, RNA, protein,alkaloids

NitrogenOrganic System Conventional System

I. Three-year study on fresh market (cv. Burbank) and processing tomatoes (cv. Ropreco) grown at UC Davis

II. Ten-year study of processing tomatoes grown at the Long Term Research on Agricultural Systems at UC Davis

A Decade of Research Evaluating the Nutrient A Decade of Research Evaluating the Nutrient Density of Organic & Conventional FoodsDensity of Organic & Conventional Foods

• Tomatoes are the second most consumed vegetable in North America– CA produced ~10 million tons of tomatoes annually (2006)

• 90% US production• 30% of global production

• U.S. consumption – Fresh tomatoes 18.1 lb per capita (2003)– Tomato products 68.6 lb per capita in (2003)

• Tomatoes are a significant nutritional source of:– Vitamins C, A and E – Carotenoids (lycopene , β-carotene)– Flavonoids [quercetin (2000 mg/annual) and kaempferol]

ERS/USDA http://www.ers.usda.gov/Briefing/Tomatoes/

Why Emphasize Tomatoes?Why Emphasize Tomatoes?

I. ThreeI. Three--Year ComparisonYear Comparison20022002--20052005

• Fields: UC Davis Student Farm– Matched certified organic (2002) and conventional fields– The fields were separated by approximately 350 feet (107 meters)– Water source and system were the same– Plants were grown using a randomized split-block design – Planting dates matched (green house and field)

• Treatments:– Organic plants received fertilization from cover crops and

composed cow manure– Conventional crops received liquid fertilizer & ammonium sulfate– Pyrellin and permithrin were applied to conventional plots

Harvesting & AnalysesHarvesting & Analyses

• Harvested at Commercial Maturity– Washed– Sorted by size and color– Sliced and vacuum packaged– Sub-samples were freeze-dried– and stored at –80 C

• The Analyses– Flavonoids

• Quercetin & Kaempferol– Percent Soluble Solids

• Sugars– Ascorbic Acid

• Vitamin C

Analysis% Increase4 % Increase4

1

Burbank Cultivar Ropreco CultivarConventional Organic Conventional Organic

Quercetin 2003 68.7 ± 5.8 b 109.0 ± 27.4 a 37.7 ± 1.3 c 60.7 ± 6.4 bc(mg / 100g DWB2) 2004 21.1 ± 2.8 ab 17.6 ± 4.1 b 22.1 ± 1.4 ab 25.1 ± 2.3 a

2005 58.4 ± 14.3 48.5 ± 11.0 47.4 ± 2.3 33.0 ± 2.7Average 49.4 ± 25.0 a 58.4 ± 46.5 a 18 35.7 ± 12.8 b 39.6 ± 18.7 b 11

Quercetin 2003 3.43 ± 0.29 bc 6.30 ± 1.58 a 2.18 ± 0.08 c 4.55 ± 0.48 b(mg / 100g WWB3) 2004 1.18 ± 0.15 1.12 ± 0.26 1.15 ± 0.07 1.44 ± 0.13

2005 3.32 ± 0.81 a 2.84 ± 0.65 ab 3.20 ± 0.16 a 2.20 ± 0.18 bAverage 2.64 ± 1.27 b 3.42 ± 2.64 a 29 2.18 ± 1.03 b 2.73 ± 1.62 b 25

Kaempferol 2003 18.8 ± 2.3 19.0 ± 5.4 15.4 ± 5.0 17.0 ± 5.7(mg / 100g DWB) 2004 27.0 ± 2.1 a 28.0 ± 1.9 a 21.6 ± 0.6 b 21.5 ± 0.4 b

2005 28.4 ± 0.7 31.9 ± 0.9 25.0 ± 2.9 28.6 ± 2.5Average 24.7 ± 5.2 ab 26.3 ± 6.6 a 6 20.7 ± 4.9 c 22.4 ± 5.8 bc 8

Kaempferol 2003 0.94 ± 0.11 1.10 ± 0.31 0.89 ± 0.29 1.28 ± 0.43(mg / 100g WWB) 2004 1.51 ± 0.12 b 1.78 ± 0.12 a 1.12 ± 0.03 c 1.23 ± 0.02 c

2005 1.61 ± 0.04 b 1.87 ± 0.05 a 1.69 ± 0.20 ab 1.91 ± 0.17 aAverage 1.35 ± 0.36 bc 1.58 ± 0.42 a 17 1.23 ± 0.41 c 1.47 ± 0.38 ab 19

A. Chassy et al J. Agric. Food Chem. 2006, 54, 8244-8252

Tomato FlavonoidsTomato Flavonoids

Soluble Solids & Ascorbic AcidSoluble Solids & Ascorbic Acid

A. Chassy et al J. Agric. Food Chem. 2006, 54, 8244-8252

Ascorbic acid 2003 13.7 ± 2.0 b 25.7 ± 7.3 a 14.2 ± 1.5 b 23.8 ± 5.6 a(mg / 100g WWB) 2004 16.0 ± 0.9 a 16.3 ± 1.2 a 11.2 ± 1.7 b 9.8 ± 1.3 b

2005 22.7 ± 1.9 24.2 ± 5.4 23.3 ± 0.8 22.1 ± 2.4Average 17.5 ± 4.7 b 22.1 ± 5.1 a 26 16.2 ± 6.3 b 18.6 ± 7.6 b 14

Ascorbic acid 2003 275 ± 40 444 ± 126 246 ± 25 296 ± 110(mg / 100g DWB) 2004 288 ± 17 a 257 ± 19 ab 215 ± 33 bc 170 ± 22 c

2005 400 ± 33 413 ± 91 344 ± 12 330 ± 35Average 321 ± 69 ab 371 ± 100 a 16 268 ± 67 b 265 ± 84 b -1

Analysis% Increase4 % Increase4

Soluble Solids 2003 4.0 ± 0.2 b1 6.0 ± 0.6 a 4.4 ± 0.3 b 5.7 ± 0.5 a(°Brix) 2004 4.8 ± 0.2 bc 5.4 ± 0.2 a 4.5 ± 0.1 c 5.0 ± 0.4 ab

2005 5.2 ± 0.3 b 5.1 ± 0.4 b 5.9 ± 0.1 a 5.4 ± 0.3 abAverage 4.7 ± 0.6 b 5.5 ± 0.5 a 18 4.9 ± 0.8 b 5.4 ± 0.4 a 9

Burbank Cultivar Ropreco CultivarConventional Organic Conventional Organic

II. II. Long Term Research on Long Term Research on AgriculturalAgriculturalSystems (LTRAS) Project at UC DavisSystems (LTRAS) Project at UC Davis

http://ltras.ucdavis.edu

• Developed 1993 to evaluate the sustainability and environmental impact of conventional and alternative agricultural systems

• 10 cropping systems in the main experiment that differ in irrigation and fertilizer (particularly N)– Irrigated conventional: fertilized corn/tomato rotation– Irrigated organic: winter legume with compost corn/tomato rotation

• LTRAS is a consistently managed system– Limits confounding factors

inherent in broad types of field studies

• e.g. mixed field and soil histories, variability in management skill, etc.

• LTRAS tomato samples are randomly collected, air-dried and archived– Yield data, soil and plant nitrogen

data, pest history, changes in key soil properties, such as organic matter, pH, salinity are monitored

The LTRAS ArchiveThe LTRAS Archive

Flavonoid Content in Haley 3155 at Flavonoid Content in Haley 3155 at LTRAS 1994LTRAS 1994--2004 2004

Quercetin

0.00

50.00

100.00

150.00

200.00

1994 1996 1998 2000 2002 2004

Year

Conc

entra

tion(

mg/

g dr

ied to

mat

o)

Conventional Organic

Kaempferol

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

1994 1996 1998 2000 2002 2004

Year

Con

cent

ratio

n(m

g/g

drie

d to

mat

o)

Conventional Organic

<0.000196.6463.3 (5.21)32.06 (1.94)Kampferol

<0.000166.3639.6 (1.58)30.2 (1.57)Naringenin

<0.0001108.16115.5 (8.0)64.6 (2.49)Quercetin

OrganicConventional

pFMeans (se)(ug g-1 DM)

Flavonoid

<0.000196.6463.3 (5.21)32.06 (1.94)Kampferol

<0.000166.3639.6 (1.58)30.2 (1.57)Naringenin

<0.0001108.16115.5 (8.0)64.6 (2.49)Quercetin

OrganicConventional

pFMeans (se)(ug g-1 DM)

Flavonoid

• 1998: SOM appeared to reach a quantitative limit of accumulation

• At this time compost application rates were reduced from 45 Mg ha-1 to 18 Mg ha-1

• It appears that the flavonoid content of tomatoes is related to the availability of soil nitrogen– Plants with limited nitrogen accumulate more

flavonoids• In organic systems N is delivered through

compost which requires mineralization prior to being taken up by the plant– Plants grow slower– Equilibrium between the synthesis of primary

and secondary plant metabolites

Quercitin

1994 1996 1998 2000 2002 2004

Flav

onoi

d co

nten

ts (m

g g-1

DM

) (19

94-1

998)

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Kaempferol

1994 1996 1998 2000 2002 20040

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tal N

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rate

(kg

ha y

r-1)

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ConventionalOrganic

Influence of Nitrogen Influence of Nitrogen ApplicationApplication

ConclusionsConclusions

• More than a decade of research investigating nutritional differences between organic and conventionally grown foods indicate that agronomic practices do impact nutrient density of foods – Increased levels of flavonoids, vitamin C and soluble

solids (sugars) in tomatoes• The greatest influence appears to be in the

relationship between soil nitrogen levels and soil nitrogen availability

AcknowledgementsAcknowledgements

• Graduate Students & Post Doctoral Scholars– Alexander Chassy, MS– Eunmi Koh, PhD– Katherine Meyers, PhD– Jaime Rudolf, PhD– Swarna Wimalasiri, PhD – Miki Heimori, PhD– Emilia Guchu, PhD

• Collaborators– Stephen Kaffka, PhD– Ford Dennison, PhD– Diane Barrett, PhD– Linh Bui, PhD– Erica Renaud, MS– Richard Bernard, PhD

• Funding– UC Division of Agriculture and Natural Resources– Seeds of Change/Mars Inc.